GEC
ST3300 & ST3400

GEC C.B. TELEPHONE
TABLE TYPE
Catalogue Nos. ST3300 series (Standard) and ST3400 series (Tropical)

Application
A table telephone of modern design, for use on all manually-operated central battery systems.

The corresponding telephone for automatic systems is described in Leaflet STL3.

Construction
The moulded Bakelite case, identical in shape with the latest British Post Office model, combines a robust design with a pleasing simplicity of line. This instrument is the same as the automatic telephone, except that a dial dummy replaces the dial, and its conversion to suit automatic systems is a simple operation.

All components are mounted on a main assembly plate, which can be withdrawn from the case very easily as a complete unit.

The cradle - switch mechanism has been specially designed to eliminate any likelihood of sticking plungers. Twin contacts give maximum reliability.

The handset is the well-known moulded Bakelite Gecophone pattern, with inset-type transmitter and receiver.

The flexible handset cord will give exceedingly long service; the conductors are made from tinsel that withstands 200,000 reciprocations without breaking.

The four - way Bakelite terminal strip, connecting the incoming line wires to the telephone cord, has moulded separators between terminal plates to maintain long leakage paths. There are separate entrances for the line wires and the cord.

Performance
The transmitter and receiver are British Post Office standards, and the high-efficiency speech circuit gives maximum volume with uniform frequency response and excellent sidetone suppression.

Tropical Pattern
G.E.C. telephones for service in tropical climates incorporate various special features, which are the result of long experience (See picture below):-

A shunt is connected across the transmitter to minimise the minute arcing that tends to occur at the granules and electrodes as the cradle switch operates ; the accelerated tendency towards frying often shown by transmitters in the tropics is thereby offset. The effect of any increase in transmitter resistance upon line circuit conditions is also minimised by the shunt. The loss in volume efficiency is very small and is partly cancelled by reduction of sidetone, the nett result being a difference of only 1 db. Should the conditions of use render the protection unnecessary and require the very maximum of volume efficiency, then the shunt may be disconnected by the simple transfer of one wire from one terminal to another.
Ventilation holes in top and bottom of the case allow air to circulate freely through the case to minimise condensation.
All apertures are covered with fine wire gauze to prevent the ingress of insects.
Metal parts are specially finished, and all wiring is specially treated, to resist the effects of high humidity and salt-laden atmospheres.
Cradle-switch springs have large insulators to ensure long leakage paths.
Flexible cord conductors are V.I.R. covered and braided overall. Since textile bindings at the ends are not in contact with the conductors, moisture absorption cannot cause leakage. Rubber fittings give mechanical protection at the points of entry to the mouldings.
All coils are specially treated to render them impervious to damp, heat and sudden changes in temperature.

Colours
The standard colour is Black but enquiries are invited for the telephone in Ivory, Jade Green or Chinese Red, with cords finished to match.

Extension Bell
A magneto extension bell in the G.E.C. Cat. No. BE1100 series (Standard) or BE1200 series (Tropical) is recommended for use with this telephone to provide calling signals at a distant point, indoors or out, or to augment calling signals in very noisy surroundings.

C.B. to Automatic
The conversion of this telephone for working on automatic systems is a simple process.

After removal of the case, the dial-dummy is replaced by a dial, and a dial cord is connected between the dial and a terminal strip on the base.

Dimensions
Length - 7.25" (18.4 cm)
Width - 9" (22.9 cm)
Height - 6" (15.2cm )
Weight - 5 lbs. 3 ozs. (2.38 kgs)

Enquiries and Orders
Please state on all enquiries and orders:

Finish - whether standard or tropical
Colour required.
If batteries are to be supplied and whether they are to be active or inert.
For component parts, please refer to item by name and quote catalogue number of complete instrument ; for example, "Handset cord for Telephone Cat. No. ST3301".

Taken from the GEC Catalogue Leaflet No. STL.5